Final answer:
To find how many of the over 20s are females on the cruise ship, first calculate the number of people over 20 using the given ratio and then apply the percentage for females. There are 75 people over 20, and 12% of them are female, resulting in 9 females over 20.
Step-by-step explanation:
The subject in question is Mathematics, specifically regarding ratios and percentage calculations. To determine how many of the over 20s are female on a cruise ship with a population of 750, where the ratio of over 20s to 20 and unders is 1:9, we must first find the number of people who are over 20. We use the ratio to do this, where 1x represents the number of over 20s and 9x represents the number of 20 and unders. Together, these must add up to 750.
1x + 9x = 750
10x = 750
x = 75
Therefore, there are 75 people who are over 20 years old on the cruise ship. Next, we are told that 12% of the over 20s are female. To calculate the number of females in the over 20 age group:
12% of 75 = 0.12 × 75 = 9
So, there are 9 females who are over the age of 20 on this cruise ship.